Instrument comprising a contact force sensor device

Abstract

A contact force sensor device ( 10 ) comprises a gas-inflatable balloon ( 20 ) 5 arranged to switch from a deflated state (D) to an inflated state (J) in which it protrudes out of a support member ( 11 ); a valve assembly ( 34 ) to inflate/deflate the gas-inflatable balloon ( 12 ) with a gas; a detector ( 41 ) of a force-related value related to a force acting on the inflated gas-inflatable balloon ( 20 ) including a membrane ( 22 ) due to a contact with a wall ( 90 ) 10 outside of support member ( 11 ); a processing unit ( 60 ) configured to receive a detection signal ( 45 ) and to consequently calculate a contact force signal ( 54 ) according to a predetermined function; and a notification device ( 70 ) configured to receive the contact force signal ( 54 ) and to notify it to a user. The value detected can be an excess pressure ΔP in gas- 15 inflatable balloon 20 , or a deformation parameter of gas-inflatable balloon 20 caused by the contact, or a strain or stress modification in membrane 22 , all these effect being caused by the contact with wall 90 . Due to its simple structure and small size, the contact force sensor device ( 10 ), can be advantageously used in an diagnostic or surgical instrument since, 20 deflated, it can be easily inserted into a patient's body through a very small entry site, possibly along with a surgical or diagnostic tool to perform a mini-invasive surgical or diagnostic operation.

The invention claimed is: 
     
       1. An instrument ( 1 , 2 , 3 , 4 , 5 , 6 , 6 ′, 7 , 8 ) comprising a support member ( 11 ) having a lateral surface ( 11 ′), and a contact force sensor device ( 10 ) that is integrated in said support member ( 11 ), said contact force sensor device ( 10 ) including:
 a gas-inflatable balloon ( 20 ) arranged to switch between a deflated state (D), and an inflated state (J) at an inflation pressure (P 0 ) and arranged to protrude from said lateral surface ( 11 ′) of said support member ( 11 ) when in said inflated state (J), 
 
       said instrument comprising:
 a feed duct ( 21 ) arranged to feed a gas to said gas-inflatable balloon ( 20 ) through a connection member ( 13 ) engaged by an entrance portion ( 23 ) of said gas-inflatable balloon ( 20 ); 
 an inflation/deflation valve assembly ( 34 ) arranged to selectively connect said gas-inflatable balloon ( 20 ) with a gas source ( 30 ) or with a gas-discharge vent ( 35 ), respectively, through said feed duct ( 21 ); 
 a detector ( 41 , 42 , 43 ) configured to output a detection signal ( 51 , 52 , 53 ) responsive to a contact force-related value related to a contact force (F) acting on said gas-inflatable balloon ( 20 ) when said gas-inflatable balloon ( 20 ) is in said inflated state (J) and is engaged in a contact (C) with a wall ( 90 ) of a body outside of said support member ( 11 ); 
 a processing unit ( 60 ) configured to:
 receive an inflate input signal from a user; 
 upon receiving said inflate input signal, cause said inflation/deflation valve assembly ( 34 ) to inflate said balloon to said inflated state (J); 
 receive said detection signal ( 51 , 52 , 53 ) and compute a contact force signal ( 54 ) responsive to said detection signal ( 51 , 52 , 53 ) according to a predetermined function; 
 wherein said function is a relationship between said contact force and said force-related value selected from the group comprised of:
 said contact pressure (P); 
 a deformation value (x,A) of said gas-inflatable balloon ( 20 ); 
 a modification of a stretch condition of said membrane ( 22 ), 
 
 said force-related value generated when said gas-inflatable balloon ( 20 ) is in contact with said wall ( 90 ), 
 receive a deflate input signal from said user; 
 upon receiving said deflate input signal, deflate said gas-inflatable balloon ( 20 ) to said deflated state (D), 
 
 a contact force-value notification device ( 70 ) configured to receive said contact force signal ( 54 ) from said processing unit ( 60 ) and to notify to a user said contact force signal ( 54 ) responsive to said contact force (F). 
 
     
     
       2. The instrument ( 1 , 2 , 3 , 4 , 5 , 6 , 6 ′, 7 , 8 ) according to  claim 1 , wherein said support member ( 11 ) comprises a recess ( 12 ), and said connection member ( 13 ) is arranged within said recess ( 12 ), said gas-inflatable balloon ( 20 ) and said recess ( 12 ) arranged in such a way that said gas-inflatable balloon ( 20 )
 is contained within said recess ( 12 ) when in said deflated state (D), and 
 protrudes from said recess ( 12 ) when in said inflated state (J). 
 
     
     
       3. The instrument according to  claim 1 , wherein said gas-inflatable balloon ( 20 ) comprises a rigid back portion ( 27 ) configured to lay on said lateral surface ( 11 ′) of said support member ( 11 ), and an inflatable front portion ( 28 ) opposite to said rigid back portion ( 27 ), wherein said entrance portion ( 23 ) protrudes from said rigid back portion ( 27 ) and has an engagement means to engage with said connection member ( 13 ). 
     
     
       4. The instrument ( 3 , 4 ) according to  claim 1 , wherein
 said gas-inflatable balloon ( 20 ) has a plurality of markers ( 24 , 25 ′, 25 ″, 26 ); 
 said detector is an image detector ( 43 ) arranged to
 detect an image of said gas-inflatable balloon ( 20 ) and of said markers ( 24 , 25 ′, 25 ″, 26 ), so as to detect a modification of said markers ( 24 , 25 ′, 25 ″, 26 ) due to said contact (C) of said gas-inflatable balloon ( 20 ) in said inflated state (J) and a wall ( 90 ); 
 output an image signal ( 53 ) as said detection signal; 
 
 said processing unit ( 60 ) comprises:
 an image-processing means configured to identify said modification of said markers ( 24 , 25 ′, 25 ″, 26 ) in said image signal ( 53 ) and to calculate said force-related deformation value (x,A) of said gas-inflatable balloon ( 20 ) due to said contact (C), as said force-related value related to said contact force (F); 
 a force-computing means configured to compute said contact force signal ( 54 ) comprising force values (F) responsive to said force-related deformation value (x,A) according to said predetermined function. 
 
 
     
     
       5. The instrument ( 3 , 4 ) according to  claim 4 , wherein said plurality of markers comprises a plurality of reference points ( 24 ), and said image-processing means is configured to:
 count a number of said reference points ( 24 ) that disappear, due to said contact (C), from a portion of said image in said image signal ( 53 ); 
 calculate said force-related deformation value (x,A) from said number of disappeared reference points ( 24 ). 
 
     
     
       6. The instrument ( 3 , 4 ) according to  claim 4 , wherein said force-related deformation value of said gas-inflatable balloon ( 20 ) is selected between:
 a flattening length (x) due to said contact (C); 
 a contact surface area (A) created by said contact (C). 
 
     
     
       7. The instrument ( 3 , 4 ) according to  claim 4 , wherein said image detector is arranged at a position selected between:
 a position outside said gas-inflatable balloon ( 20 ), and 
 a position inside said gas-inflatable balloon ( 20 ), in particular, proximate to said entrance portion ( 23 ). 
 
     
     
       8. The instrument ( 1 , 6 , 6 ′) according to  claim 1 , wherein:
 said detector is a pressure detector ( 41 ) arranged to
 detect said contact pressure (P), as said contact force-related value, between said inflation/deflation valve assembly ( 34 ) and said gas-inflatable balloon ( 20 ) when said gas-inflatable balloon ( 20 ) is contact with said wall ( 90 ); 
 output a pressure signal ( 51 ) as said detection signal; 
 
 said processing unit ( 60 ) is configured to:
 compute said contact force signal ( 54 ) comprising force values (F) responsive to said contact pressure value (P) according to said predetermined function. 
 
 
     
     
       9. The instrument according to  claim 8 , wherein said processing unit ( 60 ) is configured to calculate an excess pressure value (ΔP) equal to the difference between said contact pressure (P) and said inflation pressure (P 0 ) of said gas-inflatable balloon ( 20 ), and said function has the form:
     F=a·ΔP−b·ΔP   2    
 
       wherein a and b are parameters depending on a material and on a thickness of a membrane ( 22 ) of said gas-inflatable balloon ( 20 ), and, for a given gas-inflatable balloon ( 20 ), on said inflation pressure (P 0 ). 
     
     
       10. The instrument according to  claim 8 , wherein said processing unit ( 60 ) is configured to:
 calculate a plurality of values of an energy amount received by said instrument upon said contact (C) between said gas-inflatable balloon ( 20 ) and said wall ( 90 ) at different values of a couple of deformation parameters (x,R) of said gas-inflatable balloon ( 20 ), said energy comprising an energy portion associated to a deformation of said gas-inflatable balloon ( 20 ) and an energy portion associated to a compression of said gas within said gas-inflatable balloon ( 20 ), due to said contact (C); 
 calculate a relationship between said deformation parameters (x,R) based on an equation of state of said gas, so as to obtain said values of said energy amount as a relationship with only one deformation parameter (x,A) of said deformation parameters; 
 calculate said contact force (F) as a product between said contact pressure (P) as a relative pressure and contact surface area (A) of said gas-inflatable balloon ( 20 ) and said wall. 
 
     
     
       11. The instrument ( 2 ) according to  claim 1 , wherein
 said detector is a strain gage ( 42 ) integrally arranged along a surface of a membrane ( 22 ) of said gas-inflatable balloon ( 20 ), said strain-gage ( 42 ) configured to:
 detect said modification of a stretch condition of said membrane ( 22 ) due to a contact (C) of said gas-inflatable balloon ( 20 ) in said inflated state (J) and a wall ( 90 ); 
 output a strain signal ( 52 ) responsive to said modification of said stretch condition, as said detection signal; 
 
 said processing unit ( 60 ) is configured to compute said contact force signal ( 54 ) comprising force values (F) responsive to said strain signal ( 52 ) according to said predetermined function. 
 
     
     
       12. The instrument ( 2 ) according to  claim 11 , wherein said strain gage ( 42 ) is arranged at a position selected between:
 a position embedded in said membrane ( 22 ) of said gas-inflatable balloon ( 20 ); 
 a position on a surface of said membrane ( 22 ) of said gas-inflatable balloon ( 20 ). 
 
     
     
       13. The instrument ( 5 ) according to  claim 1 , wherein said gas-inflatable balloon is a first gas-inflatable balloon ( 20 ) and said detection signal is a first detection signal ( 53 ), and said contact force sensor device ( 10 ) also comprises:
 at least one second gas-inflatable balloon ( 20 ′) arranged to switch between a deflated state (D), and an inflated state (J), wherein said second gas-inflatable balloon ( 20 ′) is arranged to protrude from said support member ( 11 ) when in said inflated state (J), 
 a second feed duct ( 21 ′) arranged to feed a gas to said second gas-inflatable balloon ( 20 ′) through a second connection member ( 13 ) engaged by a second entrance portion ( 23 ′) of said second gas-inflatable balloon ( 20 ′); 
 
       wherein:
 said inflation/deflation valve assembly ( 34 ) is arranged to selectively connect said second gas-inflatable balloon ( 20 ′) with said gas source ( 30 ) and with said gas-discharge vent ( 35 ) through said second feed duct ( 21 ′); 
 said detector device ( 43 , 43 ′) is configured to output also a second detection signal ( 53 ′) according to a force-related value related to a second contact force (F 2 ) acting on said second gas-inflatable balloon ( 20 ′); 
 said processing unit ( 60 ) is configured to:
 receive said second detection signal ( 53 ′); 
 compute a second contact force signal ( 54 ′) according to said predetermined function. 
 
 
     
     
       14. The instrument ( 5 ) according to  claim 13 , wherein:
 said inflation/deflation valve assembly ( 34 ) is arranged to inflate said first and second gas-inflatable balloons ( 20 ,  20 ′) up to respective initial pressures (P 01 ,P 02 ) different from each other such that said first and second gas-inflatable balloons ( 20 ,  20 ′) have respective initial radiuses (R 1 ,R 2 ) equal to each other; 
 said processing unit ( 60 ) is configured to
 compute a compliance parameter (K s ) of said wall ( 90 ) according to the formula: 
 
 
       
         
           
             
               Ks 
               = 
               
                 
                   
                     F 
                     ⁢ 
                     1 
                   
                   - 
                   
                     F 
                     ⁢ 
                     2 
                   
                 
                 
                   
                     
                       F 
                       2 
                     
                     
                       π 
                       ⁢ 
                       
                         P 
                         
                           o 
                           ⁢ 
                           2 
                         
                       
                       ⁢ 
                       
                         R 
                         2 
                       
                     
                   
                   - 
                   
                     
                       F 
                       1 
                     
                     
                       π 
                       ⁢ 
                       
                         P 
                         
                           o 
                           ⁢ 
                           1 
                         
                       
                       ⁢ 
                       
                         R 
                         1 
                       
                     
                   
                 
               
             
           
         
         
           
             where
 F 1  and F 2  are forces obtained from said first and second contact force signals ( 54 , 54 ′), respectively; 
 P o1  and P o2  are said initial gas pressure within said first and second gas-inflatable balloons ( 20 , 20 ′), respectively; 
 
           
           generate also a compliance signal ( 55 ) responsive to said calculated compliance parameter (K s ); 
         
       
       wherein said contact force-value notification device ( 70 ) is configured to receive and to notify also said compliance signal ( 55 ) to said user. 
     
     
       15. The instrument ( 6 ) according to  claim 1 , wherein said contact force sensor device ( 10 ) includes at least one of:
 said feed duct ( 21 ); 
 said detector ( 41 ); 
 said processing unit ( 60 ); 
 said contact force-value notification device ( 70 ); 
 a combination thereof, 
 
       integrated in said support member ( 11 ). 
     
     
       16. The instrument ( 6 ′) according to  claim 1 , comprising a handle portion ( 29 ) and said contact force-value notification device ( 70 ) comprises an actuator ( 72 ), in particular a vibrotactile actuator, arranged at said handle portion ( 29 ), so as to provide said contact force signal ( 54 ) to said user in the form of a tactile feedback. 
     
     
       17. The instrument ( 8 ) according to  claim 1 , wherein a surgical or diagnostic tool is arranged at a distal end portion ( 14 ) of said support member ( 11 ), and said connection member ( 13 ), engaged by said gas-inflatable balloon ( 20 ) through said entrance portion ( 23 ), is arranged at a predetermined distance (L) from said distal end portion ( 14 ). 
     
     
       18. The instrument according to  claim 1 , wherein
 said support member ( 11 ) comprises a plurality of sequentially arranged phalanx support members ( 14 , 18 ) that are mutually articulated in such a way to form a robotic finger ( 17 ); 
 said gas-inflatable balloon ( 20 ) is arranged on at least one of said phalanx support members ( 18 ); 
 said processing unit ( 60 ) is configured to provide said contact force signal ( 54 ) to a drive unit of said robotic finger ( 17 ) such that said drive unit can adjust a grip force of said robotic finger ( 17 ) responsive to said contact force (F). 
 
     
     
       19. A robotic hand ( 7 ) including a plurality of robotic fingers ( 17 ) comprising the instrument according to  claim 18 . 
     
     
       20. The instrument according to  claim 1 , wherein said inflation/deflation valve assembly ( 34 ) comprises a pressure-adjustment valve ( 38 ) configured to adjust a pressure (P 0 ) of said gas provided to said gas-inflatable balloon ( 20 ) in said inflated state (J) within a predetermined range of pressures values or according to predetermined pressure values,
 in particular, said range of pressure values is set between 4 and 12 kPa.